Inkjet recording methods enable simple and inexpensive image production, and therefore have been used in a variety of printing fields. Among the inkjet recording methods, UV-curable inkjet methods are known in which droplets of UV-curable ink are landed on a recording medium and then cured by irradiation with ultraviolet rays to form an image. Recently, the UV-curable inkjet methods have been attracting attention for their capability of forming images having high rubfastness and adhesion even on recording media which lack ink absorbing properties.
In addition, as for the UV-curable inkjet method, the possibility of high-speed recording, for example, the possibility of high-speed recording by means of a single pass recording method or a high-speed serial method with fewer passes has been studied. However, performing high-speed recording involves such a problem that the interval between neighboring ink drops (dots) becomes smaller, and thus the neighboring dots are likely to combine with each other, which makes the image quality likely to be lowered. In order to prevent such combining of neighboring dots, the enhancement of pinning properties of a UV-curable inkjet ink has been studied.
As a method of enhancing the pinning properties of a UV-curable inkjet ink, it has been studied, for example, to add a gelling agent (hereinafter, also referred to as “wax”) to the ink to allow the ink to undergo sol-gel phase transition depending on temperature. That is, methods have been studied in which ink droplets are discharged in a liquid state at high temperature, and are landed on a recording medium. Concurrently with the landing, the ink droplets are cooled to be gelled, thereby preventing the combining of dots (see, e.g., PTLs 1 and 2).